Detection of substances and measurement of concentration level or indicators of various substances in a patient's blood vessels is important in health monitoring. One current non-invasive method is known for measuring the oxygen saturation of blood using pulse oximeters. Pulse oximeters detect oxygen saturation of hemoglobin by using, e.g., spectrophotometry to determine spectral absorbencies and determining concentration levels of oxygen. In addition, pulse oximetry may use photoplethysmography (PPG) methods for the assessment of oxygen saturation in pulsatile arterial blood flow based on Beer-Lambert principles. The subject's skin at a ‘measurement location’ is illuminated with two or more distinct wavelengths of light and the relative absorbance at each of the wavelengths is determined. For example, a wavelength in the visible red spectrum (for example, at 660 nm) has an extinction coefficient of hemoglobin that exceeds the extinction coefficient of oxihemoglobin. At a wavelength in the near infrared spectrum (for example, at 940 nm), the extinction coefficient of oxihemoglobin exceeds the extinction coefficient of hemoglobin. The pulse oximeter filters the absorbance of the pulsatile fraction of the blood, i.e. that due to arterial blood (AC components), from the constant absorbance by nonpulsatile venous or capillary blood and other tissue pigments (DC components), to eliminate the effect of tissue absorbance to measure the oxygen saturation of arterial blood.
Medical devices employing PPG type methods may determine concentration levels of other substances as described in U.S. Utility application Ser. No. 15/275,388 entitled, “System and Method for Health Monitoring using a Non-Invasive, Multi-Band Biosensor,” filed Sep. 24, 2016, and hereby expressly incorporated by reference herein. For example, biosensor may detect nitric oxide, liver enzymes, or other substances in blood flow using PPG techniques. PPG circuits may also be used to detect patient vitals such as heart rate, respiration rate, etc.
However, monitoring vitals and substance levels from blood flow in vitro includes many uncontrollable variables. Different substances or physiological reactive mechanisms influence blood-pressure waveforms and PPG measurements of blood substance levels. Thus, it is difficult to control testing conditions and variables in development and calibration of medical devices.
As such, there is a need during development and calibration of medical devices for a simulation system and method for blood flow and blood pressure to test various types of sensors.